1. Field of the Invention
This invention relates to a drum type washing machine with a drying function which comprises a rotating tub in which laundry is washed and dried, and more particularly to an improvement in the construction of a heat exchanger employed in such a drum type washing machine.
2. Description of the Prior Art
FIG. 5 illustrates one of conventional drum type washing machines. As shown, the washing machine comprises an outer cabinet 1, a drum-shaped water tub 2 elastically mounted on a plurality of suspension mechanisms 3 in the cabinet 1, and a drum-shaped rotating tub 4 rotatably mounted in the water tub 2. A front wall of the cabinet 1 has an access opening 5 through which laundry is put into and taken out of the rotating tub 4. A door 9 is mounted on the front wall of the cabinet 1 so as to open and close the opening 5. The water tub 2 and the rotating tub 4 nave openings 6 and 7 formed in front walls respectively. The access opening 5 is water-tightly connected by bellows 8 to the opening 6 of the water tub 2. An electric heater 17 and a blower 15 are disposed over the right-hand top of the water tub 2 so that the blower is positioned in the rear of the heater. The heater 17 comprises a heating element 16 accommodated in a duct 17a. The duct 17a has a rear end connected to a discharge side of the blower 15. The water tub 2 has a hot-air outlet 6a formed around the opening 6. The duct 17a has a front end connected via a duct 18 to the hot-air outlet 6a. 
An electric motor 11 of the outer rotor type is mounted on a generally central outside face of a rear panel 2a of the water tub 2. The motor 11 includes a rotational shaft 11a extending through a hole formed in the rear panel 2a to be fixed to the rear of the rotating tub 4. A heat exchanger 12 is provided at the left hand of the motor 11 in the rear of the water tub 2 as viewed at the rear of the machine. The heat exchanger 12 comprises a duct 18 fixed to the outside face of the rear panel 2a and having a rectangular section as shown in FIG. 6. The duct 18 has a lower end connected to a hot-air return port 13 formed in a lower portion of the water tub 2. The duct 18 further has an air outlet 14 formed in an upper end thereof and connected to a suction side of the blower 15. The blower 15, heater 17 and heat exchanger 12 constitute drying means for drying laundry.
Upon start of a drying operation, the blower 15 and the heater 17 are energized and the rotating tub 4 is rotated at low speeds alternately repeatedly in the normal and reverse directions. Further, a water supply (not shown) supplies water into the duct 18 of the heat exchanger 12. Moist air in the rotating tub 4 is then sucked into the duct 18 through holes 10 and the hot-air return port 13. The air sucked into the duct 18 is circulated through the air outlet 14, blower 15, duct 17a of the heater 17, duct 18, hot-air outlet 6a and the water tub 2 and accordingly the rotating tub 4 sequentially in this order. The air in the rotating tub 4 is warmed and dehumidified as the result of the aforesaid circulation, whereupon the laundry in the rotating tub 4 is dried.
In the above-described washing machine, the duct 18 of the heat exchanger 12 is discrete from the water tub 2. This results in a small space between the duct 18 and the water tub 2. The space increases a space defined between the rear panel 2a of the water tub 2 and the outer cabinet 1 for disposition of the heat exchanger 12. More specifically, a minimum distance, (A+2t+C), is required between the rear panel 2a of the water tub 2 and the outer cabinet 1 where A is an inside depth of the interior of the duct 18, t is a thickness of the duct 18 and C is a distance between the duct 18 and the rear panel of the water tub 2, as shown in FIG. 6. Further, a reduction in an amount of material for each component has been considered for the purpose of reduction in the manufacturing cost. Concerning the heat exchanger 12, a reduction in an amount of material for the duct 18 has been desired.
Therefore, an object of the present invention is to provide a drum type washing machine with a drying function which can reduce the space for disposition of the heat exchanger and which can reduce an amount of material for the duct of the heat exchanger.
The present invention provides a drum type washing machine with a drying function, comprising an outer cabinet, a water tub provided in the outer cabinet and having a rear wall, a generally drum-shaped rotating tub rotatably mounted in the water tub, a driving mechanism provided on a generally central outside face of the rear wall of the water tub for driving the rotating tub, and a drying unit provided for drying laundry accommodated in the rotating tub and including a heat exchanger disposed on the rear wall of the water tub so as to be positioned around the driving mechanism, the heat exchanger having a duct provided therein so that air flows therethrough, the duct including a part comprising the rear wall of the water tub.
According to the above-described construction, the duct includes a part comprising the rear wall of the water tub. Accordingly, since the heat exchanger is incorporated with the water tub, the mounting space for the heat exchanger can be reduced. Further, since the rear wall of the water tub forms-a part of the duct, an amount of material for the duct can be reduced.
In a first preferred form the washing machine further comprises, a cover mounted on an outside face of the rear wall of the water tub, and the duct comprises the cover as well as the rear wall of the water tub. The cover can easily be detached from and re-attached to the water tub when the heat exchanger is repaired.
In a second preferred form the washing machine further comprises, a cover mounted on an inside face of the rear wall of the water tub, and the duct comprises the, cover as well as the rear wall of the water tub. Even when water in the duct leaks out through a junction of the cover and the rear wall of the water tub, it is once reserved in the water tub to be discharged through a drain hole. Consequently, since a strict countermeasure need not be taken for water leakage xe2x80x9cthrough the junction, the manufacturing cost can be reduced.
In a third preferred form, the duct is mounted on the rear wall of the water tub so as to extend along a peripheral edge of the rear wall. A flow passage of air flowing through the duct can be lengthened by increasing the length of the duct. Consequently, the dehumidifying performance of the heat exchanger can be improved.
In a fourth preferred form, the wall of the water tub comprises a rear wall, the water tub includes a number of ribs mounted on the rear wall thereof to reinforce the rear wall, and the rear wall has one of two sides on which the heat exchanger is mounted and the other side on which the ribs are mounted so as to correspond to the heat exchanger. Consequently, the portion of the rear wall on which the heat exchanger is mounted can sufficiently be reinforced by the ribs as well as its portion on which the heat exchanger is not mounted. Moreover, an area of the flow passage in the duct can be prevented from being decreased as the result of provision of the ribs.
In a fifth preferred form the washing machine further comprises, a cover mounted on the rear wall of the water tub, and the duct comprises the cover as well as the rear wall of the water tub. In this construction, the duct is made of a material having a smaller sniffiness than the rear wall of the water tub. This construction permits the cover to be deformed in compliance with the configuration of the rear wall of the water tub when the cover is mounted on the rear wall. Consequently, a gap can be prevented from being defined between the cover and the wall.
In a sixth preferred form, the rear wall of the water tub is made of a synthetic resin. The synthetic resin has a better heat-insulating. Performance than metals. Accordingly, even when a part of the duct comprises the rear wall of the water tub, heat in the water tub is difficult to be transferred to the duct. Consequently, the heat exchange efficiency can be improved.